Gear pump



YOSHlNORl MORITA 2,965,039

GEAR PUMP Dec. 20, 1960 Filed March 24, 1958 5 Sheets-Sheet 1 INVENTOR g. Jyoviifi BY W ATTORNEY Dec. 20, 1960 YOSHlNORl MORITA 2,955,039

GEAR PUMP Filed March 24, 1958 5 Sheets-Sheet 2 IN VENTOR BY W ATTORNEY Dec. 20, 19 YOSHINORI MORITA 2,965,039

GEAR PUMP Filed March 24, 1958 ATTORNEY Dec. 20, 1960 YOSHINORI MORITA 2,965,039

GEAR PUMP Filed March 24, 1958 5 Sheets-Sheet 4 fi N12 'O oa f j INVENTOR' o'u'ii' Dec. 20, 1960 OOOOOOOOOOOOO TA 2,965,039

United States Patent GEAR PUMP Yoshinori Morita, 67 HigashhTerahara, Kumamotoshi, Japan Description of invention This invention relates to a gear pump. The object of the invention is the rotation of interior and exterior gears with. the constant and complete contact at the top or at points-on the profile of both gears. T he principle of the invention is that the profile of both gears are hypo-cyloid envelopes and the interior gear has one tooth less thanthe exterior gear.

in ordinary types of gear pumps, the construction of the gears is simple and: they are also standardized; This? is convenient in various: ways, but the minimum. number of teeth that theoretically cannot. be under cutis 32 in the pressure angle 14 /2, 18 in the pressure angle 14 in the stub gear at pressure angle 20. Consequently the pump using such gears must be. of large construction.

Since the number of gears has no direct influence to the pumping volume, various designs are made to mini mize the number of gearteeth, hencethe appearance of the trocoid pumps.

However the trocoid pumps now in use have not the true trocoid curves but they are only the imitation with the curves made of circular lines, furthermore due to the difficulty of creating the .tooth shape, it is usually cut with breaching machines. It is a well known fact that the manufacturing cost is not only; high but there are gaps in the engagement of both gears. Hence it is not possible to reduce the number of revolutions less than a fixed value, therefore the efficiency is not high.

In this invention, adopting the aforesaid principle, the pump using the gears with the shape surrounded by the curves that are simple to create, the interior gear contacting closely at the top with the exterior gear or at a profile of the former contacting closely with the profile. o'f'the later. It. reduces. the construction cost and maintainsv high efiic'iency at the desired speed. It carries out the. duty. as. the pump and in addition it accomplishes thevwork, of prime mover of fluid in its reverse action.

Description-01E drawings The-following descriptions are given for. the drawings of this invention;

Fig; 1' is the elevational section of the gear pump. of this invention. This is a general showing of the invention.

Fig. 2 is the cross-sectional plan view at X-X of the Fig. 1.

Fig. 3 shows the relationship between the hypo cycloid 2,965,039 Patented Dec. 20, 1960 Fig. 7 gives the detail of the cyclo curve of the interior gear.

Fig. 8 gives the detail of the cyclope curve of interior gear.

Fig. 9 illustrates that four top or peak points of the cyclo curve of the interior gear are on the cyclo curves of the exterior gear when both gears are rotating in em gagement; also it shows the condition when one of the tops of the cyclo curve of the interior gear overlaps one of the tops of the cyclo curve of the exterior gear.

Fig. 10 shows the condition when the main shaft turns toward the left in .p Radian in the embodiment shown in the Fig. 9-.

Fig. 11 gives the detail when a point of the cyclo curve of the exterior gear contacts with a point of the cyclo curve of the interior gear in the embodiment shown in a the Fig. 10.

Fig. 12 is the elevational section of a preferred type of the gear pump of this invention (3 toothed exterior gear, 2 toothed interior gear).

Fig. 13 is the section at Y-Y in the Fig. 12.

Fig. 14 shows the relationship between the envelope curve which is the combination curve of the hypo cycloid envelope (that is the curve of the tooth shape of the exterior gear with the arc line in the embodiment of the Fig. 13). It shows the relationship between the basic hypo cycloid and the cycle curve, the relationship between the bar with the arcs at both endswhich form the tooth shape curve of the interior gear and its basic straight line.

Fig. 15 is the elevational section of this gear pump of the preferred embodiment of this invention (2-toothed,

' exterior gear and I-toothed gear).

Fig. 16 is the section of Fig. 15 at Z Z.

Fig. 17 illustrates the relationship of the interior gear and the exterior gear in the state of Fig. 16.

In the drawings:

- 1- is the 5 -t oojthedexteriorgear,

envelope in combination with the outer arc or-c'yclopex curve, which is the curve of the tooth shape of'the interior and exterior gears in the embodiment of Fig. 2, and the hypo cycloid curve cyclo curve and its basic circle P and Q.

Fig. 4 illustrates'the locus of contact point of both the interior and exterior gears shown in the Fig. 3.

Fig. 5 gives the detail of the-cyclo curve of the exterior gear.

terior. gear.-

Fig. 6 gives the detail of the cyclope curve of the ex- 7 lf'is the 3 -toothed exterior gear;

1" is the 2-toothedexterior gear, 2. isthe 4- toothed interior gear;

2. is the 2-toothed interior gear, and 2" is the l-toothedinterior gear.

The casing 5 is'shown in cross-section; the port 3r becomes an inlet when the shaft turned to the right (clockwise), and becomes an outlet when it is turned? to the left (counterclockwise). Similarly, the port 4 becomes an outlet when itis turned to the. right, and an inlet when it is turned to the left. 6 is the shaft fixed to the interior gear.

Detailed description In the operation of the pump, when the mainshaft 6 is revolved to the right, it will drive the interior gear 2 rightward in revolution; the exterior gear is driven by the interior gear. In this case, the spaces 7" and 8 formed by the interior and exterior gears among spaces 7, 8, 9, 10, 11 will be enlarged along with the: rightward revolution, inletting the fluid through port 3.

The mark 9 shows the condition when these:-spaee's reach the maximum. As shown in the Fig. 2, the side ports 3 and 4 are both isolated in the state of the space 9.

As the rightward revolution continues, the space is connected to the side port 4 and the spaces 10, 11 will get smaller and the fluid filled here is forced out through the side port 4. As shown in the Fig. 3, the aforesaid spaces 7,8; 9,, 10-, 11-shal-l5 bezisolatedi,

The cyclocurve a} which. is the base of the cyclope 7 and its locus shall be the circle 22 as indicated in Fig. 11 and stated in the later paragraph.

Now that a point on the curve A corresponding to the point 12 on the curve a is the point 17,-and a point on the curve B corresponding to the point 12 on the curve A is also the point 17. Similarly 18, 19, 20, 21 are the contact points of the curve A and the curve B. It is obvious that these points certainly exist.

The following descriptions are given about the curves of the tooth shapes. j

r represents the semi-diameter of the rolling circle of the exterior gear that produces the hypocycloid curve a, and equally the semi-diameter of the rolling circle of in-, terior gear that produces the hypocycloid curve b. Their circumferences of the basic circles Q and P shall be 21rr N and 21rr Xn. (n and N are the positive numbers that indicate the number of teeth of the interior and exterior gears.) Hence the semi-diameters of the base circles Q and P will be represented by Nr and nr Therefore, the semi-diameters of the circle Q, that is, in the Fig. 5 is 5r When the rolling circle p rolls from the point Q on the base circle Q without sliding in close contact inside of Q, the locuses Q;Q Q Q Q Q are drawn by the point a on the rolling circle form the cyclo curve a.

These are expressed by following equations:

X=r (4 cos 8+cos 45) (1) =r (4 sin 6sin 46) Generally X=r (M cos B-l-cos M6) (2) Y=r (M sin 6--sin M6) Where:

7 M=N-1 6 ,,=Center angle formed by adjoining tops of the curve a.

Fig. 6 shows the cyclope curve A. Locus is drawn by the circumference of the travelling circle when the travelling circle R has the semi-diameter r with its center on the cyclo curve a. This envelope curve will be a semicircumference expressed by gi, when the travelling circle R is at Q. In the course of travelling toward the Q it draws the curve ij. At the Q it becomes to semi-circumference ik.

The equations for the envelope curve ii are:

Fig. 7 is the cyclo curve b. The semi-diameter of the base circle Q of the curve a is Nr or 5r but in the curve b, the semi-diameter of the base circle P is (N l)==nr or 4r The equations are:

X=r (3 cos +cos 30)=4r cos 39 Y=r (3 sin 9--sin 30) =4r cos s cyclo curve.

Where! 0 Center angle formed by the adjoining tops on the curve I).

ZI n Fig. 8 shows the cyclope curve B. The equations are:

X=4r cos 36ir sin 0 (6) Y=4r sin Mir cos 6 Now the detailed descriptions are given that each top or peak on the curve b shall be on the curve a.

Fig. 9 shows the relation with the curve -a when Q that is one of the tops of the curve a, overlaps with a top of the curve bP P P P Now let us prove that P, is on the curve :1.

Draw a line 0 2 from the center of the base circle Q, that is, 0 parallel to straight connecting line from the center 0 of the base circle P to the P Draw 'a'circle of'semi-diameter r, with the center at point p where 0 0 :0 12 and then connect p and P pi; and 0 0 lines shall be parallel. As pP equals to r the circle pwith the center at p and with the semi-diameter r will contact internally with the base circle Q which is a condition of a rolling circle that forms the curve a.

If the P at a point on the rolling circle p, the (travelling angle at circumference of the rolling circle) is' 5 times of the 'y (travelling angle at the center of therolling circle which is generally expressed as N times), the P ought be on the curve a. The equations are:

' It can be seen that P is in the way from Q to Q;, on the In similar way, the other points P and P can be proved that they are on the same curve.

Fig. 10 shows the condition in the Fig. 9 with the shaft 6 and its center (0 From this figure, it can be proved that P, is on the curve between Q and Q; in the following way.

As in the Fig. 9, draw a parallel line from O to 0 1 select a point p, where 0 p =nr then connect p and P Draw a circle with the center at p with semi-diameter 1- It can be seen that this circle is one of the conditions of the rolling circle, the same as in the last figure. Then draw a line O Q O Q forming a with O Q Whereas:

From the Equations 11 and 12,

Hence P, is on the curve a between Q, and (1,. Other points can be proved with similar procedures. Thus it is made plain that each top of the curve'b is alwaysyon the curve a.

Next, the following explanations are given about the contact point 12 in the Fig. 3.

Fig. 11 shows the curve a, curve b, contact point, 12 and its locus the circle 22 with its center at point Point 0 is on the extended line of 0 0 at O and semi-diameter r with the base circle Q and base circle P. It is one of the conditions of the rolling circle of the curve b.

Draw a straight line 0 12 from the 0 of the O P the same as ,u toward the left. Its intersection with the circle 0 is marked as the point 12.

Whereas:

This point 12 is a point located on the curve b from P to P,,. Then draw a line 0 Q from 0 that will form a with O P Whereas:

n B- N Let Q be an intersection of O Q and the base circle Q. Then the point on the rolling circle when it is positioned at 0 on the curve a from Q to Q is at the point turned leftward to the extent of Na from the line O P From the Equations 13 and 14, the relation of Na and a can be obtained as follows:

Since the point 12 is a point on the curve a and also is a contact point of the curve a and the curve b, its locus shall of course be the circle 0 From the above reasoning, it is obvious that points 12, 13, 14, 15, 16, shall certainly exist.

As the point 12 is an important point in this invention, the locus of its corresponding point 17 (Fig. 3) is shown in the Fig. 4. Various points of the point 12 are expressed as 12,,, 12 12 etc., and its corresponding points 17 are expressed as 17,,, 17 17 etc. Ordinarily the semi-diameter r of the rolling circle is larger in construction than the semi-diameter r of the travelling circle, so its maximum distance of both locuses shall be- The distance between the side port 3 and 4 is expressed by mark h in the Figs. 1, 13 and 16.

With above descriptions, it is made plain that the type of gear pump is obtainable which revolves Without friction, a top or a profile of the interior gear contacting closely with the profile of the exterior gear at all times, having the tooth shape curve surrounded by the hypocloid envelope, the interior gear having one tooth less than the exterior gear.

Maintaining the difierence of one tooth between the interior and exterior gears in the number of teeth, if the number is reduced in steps down to 3-toothed exterior gear and 2-toothed interior gear, the base circle semidiameter of the exterior gear shall be 3 times of the rolling circle, the base circle semi-diameter of the interior gear shall be 2 times of the rolling circle. As the basic curve of the tooth shape of the exterior gear is the locus drawn by a point of the rolling circle when the rolling circle with /3 diameter of the basic circle of the exterior gear rolls on the base circle of the exterior gear, even though its nature and style are both the cyclo curve, as the basic curve of the tooth shape of the interior gear is the locus drawn by a point of the rolling circle when a rolling circle with V2 semi-diameter of the base circle rolls on the base circle, the nature of this curve is a cyclo curve but'only the-style is changed, into a straight line.

The inter-relation of the cyclope curve and the cyclo curve and the base curve of the interior and exterior gears is shown in the Fig; 14. When; this; is. applied to a pump, it turns into a preferred type as shown in the Fig. 12 and 13. Beside the above, if the number of teeth of the exterior gear'isreduced to '2, and theinterior gear teeth reduced to 1, the basic curve of the tooth shape of the exterior gear will be the locus drawn by; a point of the rolling circle, will be a straight line"; the basic curve of the tooth shape of the interior gearwill be a locus drawn by a point of the rolling circle-when the rolling circle of the equal semi-diameter rolls on the base circle of the interior gear, which turns out to be a point.

The inter-relation between the cyclope curve, the cyclo curve and the base circle of both interior and exterior gears is shown in the Fig. 17, and when the principle is applied in the pump, it will be a preferred embodiment as shown in the Figs. 15 and 16. There is no change in the composition of the basic curves of the interior and exterior gears and in the difierent number of teeth of interior and exterior gears, but they are only the changed styles. The inter-relation of both gears for the ordinary types can be applied to these changed types. Therefore the pump adopting the principle of this invention will operate at high efiiciency and also operate in reverse action of the pumping.

It should be noted that the gear pump of this invention can be used as fluid prime mover with high efficiency.

Preferred embodiments of the invention have been described. Various changes and modifications however may be made within the scope of the invention as set forth in the appended claims.

I claim:

1. A rotary mechanical pump comprising an exterior gear having teeth arranged along a base circle, an interior gear having one tooth less than the teeth of the exterior gear and arranged along another base circle, said gears mounted eccentrically to each other in sealing contact and positioned to have a point of full mesh, each of the said gears having contours defining a cyclope curve formed by their respective teeth as generated by a travelling circle having a radius r with its center travelling along a respective cyclo curve for defining the outer envefope thereof, each of said respective cyclo curves being generated by a point on the circumference of a rolling circle having a radius r said point moving from one point on the respective base circle of the gears to another point on the respective base circle of the gears as the rolling circle rolls along the interior of the circumference of the respective base circle of the gears, all points on the respective cyclo curve being within or on the respective base circle, and an inlet port and an outlet port each in a side of the pump and separated by a land therebetween, said land separating the ports by a distance it on the side of full mesh of the gears, said land being centered on a radius of the base circle of the exterior gear and said radius intersecting said point of full mesh, the relationship of the radii r; and r, and the distance h being such that when 2. The rotary mechanical pump of claim 1 wherein when the diameter of the rolling circle for generating the cyclo curve is one-half of the diameter of the base circle thereof for the interior gear, then the teeth on the interior gear shall be two.

3. The rotary mechanical pump of claim 1 wherein when the diameter of the rolling circle for generating the 7 eyc'lo' curve of the interior gear is equal to the diameter of the base circle thereof for the interior gear, then the teetli'o'n the interior gear shall be one.

References Cited in the file of this patent I UNITED STATES PATENTS Re.21,316 Hill Jan. 9, 1940 r 457,294 Tilden Aug. 4, 1891 1,682,563 Hill Aug. 28, 1928 1,682,564 Hill .Q Aug. 28, 1928 1,682,565 Hill Aug. 28, 192$ 1,798,059 Bilgram et a1. Mar. 24, 1931 Hill Dec. 1, 1931 Hill Aug. 31, 1937 "Hill Nov. 27, 1945 Hill et.a1. Apr. 3, 1951 Hill et a1. June 24, 1952 Hill'et a1. Jan. 19, 1954 OTHER REFERENCES Kinematics of Gerotors, by Myron F. Hill, 1927 (44 

